USGS/SLU Moment Tensor Solution ENS 2020/06/19 20:42:21:0 38.17 -117.83 6.5 4.9 Nevada Stations used: BK.DANT BK.LEGD BK.OVRO BK.SUTB BK.WELL BK.WINE CI.CCC CI.CLC CI.CWC CI.FUR CI.GRA CI.GSC CI.HAR CI.ISA CI.LRL CI.LUC2 CI.MWC CI.OSI CI.RAG CI.TIN CI.TPO CI.VES GS.MCA04 IM.NV31 LB.TPH NC.AFD NC.LDH NC.MDPB NN.BEK NN.CMK6 NN.CTC NN.DSP NN.GMN NN.KVN NN.LHV NN.MCA06 NN.MPK NN.PAH NN.PIO NN.PNT NN.PRN NN.Q09A NN.QSM NN.REDF NN.S11A NN.SHP NN.WAK NN.WDEM NN.WLDB SN.HEL US.ELK US.TPNV UU.CCUT UU.LCMT UU.PSUT UU.SZCU UU.VRUT Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 7.08e+22 dyne-cm Mw = 4.50 Z = 10 km Plane Strike Dip Rake NP1 196 85 -165 NP2 105 75 -5 Principal Axes: Axis Value Plunge Azimuth T 7.08e+22 7 330 N 0.00e+00 74 214 P -7.08e+22 14 62 Moment Tensor: (dyne-cm) Component Value Mxx 3.69e+22 Mxy -5.82e+22 Mxz -4.37e+20 Myy -3.39e+22 Myz -1.90e+22 Mzz -3.09e+21 #############- T #############------ ### ############---------- ##################------------ ####################-------------- ####################------------ - ####################------------- P -- #####################------------- --- -###################-------------------- ----#################--------------------- --------############---------------------- ------------#######----------------------- -----------------##----------------------- -----------------######----------------- -----------------####################### ---------------####################### --------------###################### -------------##################### ----------#################### ---------################### ------################ -############# Global CMT Convention Moment Tensor: R T P -3.09e+21 -4.37e+20 1.90e+22 -4.37e+20 3.69e+22 5.82e+22 1.90e+22 5.82e+22 -3.39e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20200619204221/index.html |
STK = 105 DIP = 75 RAKE = -5 MW = 4.50 HS = 10.0
The NDK file is 20200619204221.ndk The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution ENS 2020/06/19 20:42:21:0 38.17 -117.83 6.5 4.9 Nevada Stations used: BK.DANT BK.LEGD BK.OVRO BK.SUTB BK.WELL BK.WINE CI.CCC CI.CLC CI.CWC CI.FUR CI.GRA CI.GSC CI.HAR CI.ISA CI.LRL CI.LUC2 CI.MWC CI.OSI CI.RAG CI.TIN CI.TPO CI.VES GS.MCA04 IM.NV31 LB.TPH NC.AFD NC.LDH NC.MDPB NN.BEK NN.CMK6 NN.CTC NN.DSP NN.GMN NN.KVN NN.LHV NN.MCA06 NN.MPK NN.PAH NN.PIO NN.PNT NN.PRN NN.Q09A NN.QSM NN.REDF NN.S11A NN.SHP NN.WAK NN.WDEM NN.WLDB SN.HEL US.ELK US.TPNV UU.CCUT UU.LCMT UU.PSUT UU.SZCU UU.VRUT Filtering commands used: cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3 Best Fitting Double Couple Mo = 7.08e+22 dyne-cm Mw = 4.50 Z = 10 km Plane Strike Dip Rake NP1 196 85 -165 NP2 105 75 -5 Principal Axes: Axis Value Plunge Azimuth T 7.08e+22 7 330 N 0.00e+00 74 214 P -7.08e+22 14 62 Moment Tensor: (dyne-cm) Component Value Mxx 3.69e+22 Mxy -5.82e+22 Mxz -4.37e+20 Myy -3.39e+22 Myz -1.90e+22 Mzz -3.09e+21 #############- T #############------ ### ############---------- ##################------------ ####################-------------- ####################------------ - ####################------------- P -- #####################------------- --- -###################-------------------- ----#################--------------------- --------############---------------------- ------------#######----------------------- -----------------##----------------------- -----------------######----------------- -----------------####################### ---------------####################### --------------###################### -------------##################### ----------#################### ---------################### ------################ -############# Global CMT Convention Moment Tensor: R T P -3.09e+21 -4.37e+20 1.90e+22 -4.37e+20 3.69e+22 5.82e+22 1.90e+22 5.82e+22 -3.39e+22 Details of the solution is found at http://www.eas.slu.edu/eqc/eqc_mt/MECH.NA/20200619204221/index.html |
Regional Moment Tensor (Mwr) Moment 6.579e+15 N-m Magnitude 4.48 Mwr Depth 11.0 km Percent DC 90% Half Duration - Catalog US Data Source US 2 Contributor US 2 Nodal Planes Plane Strike Dip Rake NP1 102 84 -8 NP2 193 82 -174 Principal Axes Axis Value Plunge Azimuth T 6.744e+15 N-m 1 148 N -0.344e+15 N-m 80 245 P -6.400e+15 N-m 10 57 |
Regional Moment Tensor (Mwr) Moment 5.755e+15 N-m Magnitude 4.44 Mwr Depth 8.0 km Percent DC 98% Half Duration - Catalog NN Data Source NN 1 Contributor NN 1 Nodal Planes Plane Strike Dip Rake NP1 197 82 -163 NP2 104 73 -9 Principal Axes Axis Value Plunge Azimuth T 5.790e+15 N-m 6 330 N -0.072e+15 N-m 71 222 P -5.719e+15 N-m 18 61 |
(a) ML computed using the IASPEI formula for Horizontal components; (b) ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.
(a) ML computed using the IASPEI formula for Vertical components (research); (b) ML residuals computed using a modified IASPEI formula that accounts for path specific attenuation; the values used for the trimmed mean are indicated. The ML relation used for each figure is given at the bottom of each plot.
The focal mechanism was determined using broadband seismic waveforms. The location of the event and the and stations used for the waveform inversion are shown in the next figure.
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The program wvfgrd96 was used with good traces observed at short distance to determine the focal mechanism, depth and seismic moment. This technique requires a high quality signal and well determined velocity model for the Green functions. To the extent that these are the quality data, this type of mechanism should be preferred over the radiation pattern technique which requires the separate step of defining the pressure and tension quadrants and the correct strike.
The observed and predicted traces are filtered using the following gsac commands:
cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT WVFGRD96 1.0 105 75 10 4.13 0.2736 WVFGRD96 2.0 105 70 15 4.26 0.3638 WVFGRD96 3.0 105 75 5 4.29 0.4040 WVFGRD96 4.0 105 75 5 4.33 0.4335 WVFGRD96 5.0 105 75 -5 4.36 0.4598 WVFGRD96 6.0 105 75 -5 4.39 0.4824 WVFGRD96 7.0 105 75 -10 4.43 0.5011 WVFGRD96 8.0 105 75 -10 4.46 0.5161 WVFGRD96 9.0 105 75 -10 4.49 0.5251 WVFGRD96 10.0 105 75 -5 4.50 0.5289 WVFGRD96 11.0 105 75 -5 4.52 0.5282 WVFGRD96 12.0 105 80 -5 4.53 0.5243 WVFGRD96 13.0 105 80 0 4.54 0.5179 WVFGRD96 14.0 105 80 0 4.55 0.5099 WVFGRD96 15.0 105 80 0 4.56 0.4999 WVFGRD96 16.0 105 80 0 4.57 0.4897 WVFGRD96 17.0 105 80 5 4.58 0.4784 WVFGRD96 18.0 105 80 5 4.59 0.4675 WVFGRD96 19.0 105 80 5 4.60 0.4570 WVFGRD96 20.0 105 80 5 4.60 0.4464 WVFGRD96 21.0 105 80 5 4.61 0.4356 WVFGRD96 22.0 105 80 5 4.62 0.4256 WVFGRD96 23.0 105 75 5 4.62 0.4161 WVFGRD96 24.0 105 75 5 4.62 0.4069 WVFGRD96 25.0 105 75 5 4.63 0.3981 WVFGRD96 26.0 105 75 5 4.64 0.3900 WVFGRD96 27.0 105 75 5 4.64 0.3823 WVFGRD96 28.0 105 75 5 4.65 0.3749 WVFGRD96 29.0 105 75 5 4.65 0.3677
The best solution is
WVFGRD96 10.0 105 75 -5 4.50 0.5289
The mechanism correspond to the best fit is
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The best fit as a function of depth is given in the following figure:
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The comparison of the observed and predicted waveforms is given in the next figure. The red traces are the observed and the blue are the predicted. Each observed-predicted component is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. A pair of numbers is given in black at the right of each predicted traces. The upper number it the time shift required for maximum correlation between the observed and predicted traces. This time shift is required because the synthetics are not computed at exactly the same distance as the observed and because the velocity model used in the predictions may not be perfect. A positive time shift indicates that the prediction is too fast and should be delayed to match the observed trace (shift to the right in this figure). A negative value indicates that the prediction is too slow. The lower number gives the percentage of variance reduction to characterize the individual goodness of fit (100% indicates a perfect fit).
The bandpass filter used in the processing and for the display was
cut o DIST/3.3 -40 o DIST/3.3 +50 rtr taper w 0.1 hp c 0.03 n 3 lp c 0.07 n 3
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Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to thewavefroms. Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure. |
A check on the assumed source location is possible by looking at the time shifts between the observed and predicted traces. The time shifts for waveform matching arise for several reasons:
Time_shift = A + B cos Azimuth + C Sin Azimuth
The time shifts for this inversion lead to the next figure:
The derived shift in origin time and epicentral coordinates are given at the bottom of the figure.
Thanks also to the many seismic network operators whose dedication make this effort possible: University of Nevada Reno, University of Alaska, University of Washington, Oregon State University, University of Utah, Montana Bureau of Mines, UC Berkely, Caltech, UC San Diego, Saint Louis University, University of Memphis, Lamont Doherty Earth Observatory, the Oklahoma Geological Survey, TexNet, the Iris stations, the Transportable Array of EarthScope and other networks.
The WUS.model used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01 Model after 8 iterations ISOTROPIC KGS FLAT EARTH 1-D CONSTANT VELOCITY LINE08 LINE09 LINE10 LINE11 H(KM) VP(KM/S) VS(KM/S) RHO(GM/CC) QP QS ETAP ETAS FREFP FREFS 1.9000 3.4065 2.0089 2.2150 0.302E-02 0.679E-02 0.00 0.00 1.00 1.00 6.1000 5.5445 3.2953 2.6089 0.349E-02 0.784E-02 0.00 0.00 1.00 1.00 13.0000 6.2708 3.7396 2.7812 0.212E-02 0.476E-02 0.00 0.00 1.00 1.00 19.0000 6.4075 3.7680 2.8223 0.111E-02 0.249E-02 0.00 0.00 1.00 1.00 0.0000 7.9000 4.6200 3.2760 0.164E-10 0.370E-10 0.00 0.00 1.00 1.00
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files: